1. Field of the Invention
The present invention relates to disc apparatuses in which optical discs such as CDs and DVDs, magnetic optical discs, or magnetic discs are clamped to rotate, and particularly, to a disc apparatus that controls the movement of a head and performs clamping and unclamping of a disc based on a driving force of a common motor.
2. Description of the Related Art
Generally, when a disc is inserted into a casing of an in-vehicle disc apparatus in a stand-by mode, the disc is transferred by, for example, a transfer roller so that the center of the disc is clamped onto a rotator (a turntable). This switches the stand-by mode to a disc-driving mode. In the disc-driving mode, the rotator spins the disc, and a head facing the recorded face of the disc moves parallel to the disc. Thus, the head reads data recorded on the disc, or records data onto the disc.
In a disc apparatus of this type, it is necessary to move a switch slider with the driving force of a motor so as to unclamp the disc from the rotator for stand-by mode or to clamp the disc onto the rotator for disc-driving mode. Moreover, in the stand-by mode, the transfer roller must be driven with a motor that transfers the disc into the casing or ejects the disc out of the casing when the disc is unclamped from the turntable. On the other hand, in the disc-driving mode, it is necessary to drive a sled mechanism with the driving force of a motor to move the head parallel to the recorded face of the disc.
Accordingly, in such a disc apparatus, each mechanism must be driven by a corresponding motor. For this reason, if there are multiple motors installed in the disc apparatus, manufacturing costs and the weight of the apparatus increases. To solve such problems, U.S. Pat. No. 6,411,582 discloses a disc player that drives the mechanisms with a single motor.
The disc player disclosed in U.S. Pat. No. 6,411,582 includes a driving gear (a worm wheel) driven by a motor; and a switch-control idler gear and a roller-actuating idler gear, which are both engaged with the driving gear. Both idler gears are supported by an idler plate. The idler plate is rotatable such that both idler gears are capable of revolving around the driving gear while being engaged with the driving gear.
In the disc-driving mode, the idler plate is locked by an idler-locking plate. Moreover, in the disc-driving mode, the switch-control idler gear engages with a pickup-feeding gear, and the roller-actuating idler gear disengages from a transfer-roller-actuating gear. Consequently, the driving force of the motor moves a pickup parallel to the disc.
When the pickup moves toward the center of the disc, the pickup presses the idler-locking plate such that the idler plate becomes unlocked from the idler-locking plate. Both idler gears thus revolve around the driving gear such that the switch-control idler gear disengages from the pickup-feeding gear and then engages with a switching gear. This drives a shift plate, and the moving force of the shift plate unclamps the disc. Moreover, the roller-actuating idler gear engages with the transfer-roller-actuating gear, thus driving the transfer roller. Consequently, this ejects the unclamped disc out of the disc player.
In conventional disc players, the shift plate is provided with a locking slot. The locking plate and the locking slot regulate the rotational position of the idler plate.
The conventional disc player described above has the following problems:
(1) In the disc-driving mode, the idler-locking plate locks the idler plate so as to maintain the engagement state between the switch-control idler gear and the pickup-feeding gear. For switching from disc-driving mode to stand-by mode, the pickup is moved towards the center of the disc. The moving force of the pickup presses the idler-locking plate towards the inner portion of the disc so that the idler plate becomes unlocked from the idler-locking plate.
However, because the idler-locking plate is biased towards the outer periphery of the disc by a spring, that is, towards the locking direction, the pickup in the stand-by mode constantly presses against the idler-locking plate, namely, against the biasing force of the spring. This implies that if the engagement between the pickup and a leading screw, which applies feeding force to the pickup, becomes loose due to, for example, external vibration, the biasing force of the spring may move the idler-locking plate and the pickup toward the output periphery of the disc. Consequently, this may be problematic due to the fact that the position setting of the idler plate may become different from the intended position in the stand-by mode.
(2) As described previously, the shift plate is provided with the locking slot, and the locking plate and the locking slot regulate the rotational position of the idler plate. In other words, the locking slot restricts the idler plate from rotating to maintain the engagement state between the switch-control idler gear and the switching gear, and between the roller-actuating idler gear and the transfer-roller-actuating gear. Furthermore, when the shift plate is moved and the idler plate becomes free of the restriction of rotation, the idler plate rotates and the switching gear engages with the pickup-feeding gear. Thus, in this state, the locking plate locks the idler plate.
Accordingly, this may be problematic in view of the fact that the disc player requires a large number of components because the positioning of the idler gears is regulated by both the locking slot and the locking plate of the shift plate. Moreover, if the movement of one of the shift plate and the locking plate is slower than the other to cause a time lag, it may cause difficulties in switching between the two modes.
(3) In the conventional disc player described above, the roller-actuating idler gear is constantly engaged with the transfer-roller-actuating gear when the switch-control idler gear is engaged with the switching gear. This means that, after the central hole of the disc is aligned with the rotator, the transfer roller continues to rotate until the shift plate moves and the clamping of the disc is completed. It is thus possible that the rotating transfer roller could damage the disc in this time period.
(4) As described previously, the idler plate supports both the switch-control idler gear and the roller-actuating idler gear. A driving force is applied to the idler plate and each of the idler gears so that both idler gears revolve around the rotating driving gear. This requires a great amount of power because a large amount of driving force is required for rotating the driving gear and the motor must thus be driven continuously.